1. Field of the Invention
The present invention relates to a device for holding borehole formation cores under a drill press which bores the cores to produce core samples for fluid flow testing.
2. Discussion of the Prior Art
It is common in the hydrocarbon exploration and production field to take a formation core sample from a borehole and analyze it for various subsurface formation properties and to produce data which is useful for hydrocarbon drilling and/or recovery operations. In a typical case, a larger formation core sample, e.g., 6" in diameter and 9-12" long, is taken in the field and sent to a laboratory for analysis. Because of the different experiments which may be performed on the core sample, it is also common to produce a number of smaller core samples for testing from the larger core sample. To do this, the larger core sample is typically bored at a plurality of locations to produce a plurality of core samples.
A vise-type holding device having jaws, at least one of which is movable, is generally used to hold the larger core sample under a drill press during boring. Although the jaws can reciprocally move relative to one another, they are otherwise limited in their freedom of movement, making it difficult to properly hold the larger core sample in different positions for boring. In addition, it is often difficult to hold large irregularly shaped or flat core samples between the jaws. If the core sample is not properly secured during boring, damage to the core sample may result. Finally, the jaws are typically reciprocally moved by a hand-operated mechanical screw mechanism which is slow and cumbersome to operate and which makes it difficult to precisely control the pressure applied to the core sample. Too much pressure may cause the sample to crack or break, while too little pressure could cause the sample to slip and be damaged during a boring operation.